Error on the example format

As example, the command should be like:
`$ ./bin/hash-files -f '["package.json"]' -a sha256`

But it would throw an error said `Option "files" has a value that cannot be converted to an Object/Array: [package.json].`

It should be `$ ./bin/hash-files -f '[\"package.json\"]' -a sha256` instead.